Gamma irradiation test of Ge-doped single-mode optical fiber at cryogenic conditions

Optical fibers are used routinely in harsh environments for signal transmission or sensing applications. Whereas the individual challenges originating from very high or very low temperatures, vacuum or ionizing radiation were extensively studied, the effects of combinations of these conditions were not investigated widely. In this paper we report on a detailed analysis of gamma irradiation tests done on Germanium-doped single-mode fibers at very low temperatures of 16 K. The drastic change in radiation response is shown with varying temperatures through measurements with discrete light sources and a spectral measurement system. To monitor the temperature in the fibers, Fiber-Bragg-Gratings (FBG) were used and their response under radiation observed. The findings will be valuable for determination of the temperature dependence of the point-defect formation as well as for specialized applications at low temperatures, such as accelerators or deep space missions.